RU2587449C1 - Method of cleaning sulphate or nitrate solutions from chloride-ion - Google Patents

Abstract

FIELD: metallurgy; chemistry.

SUBSTANCE: chloride-containing process solution is brought into contact with hypochloric acid solution in tributyl phosphate. Chloride ion is oxidised to form elementary chlorine, and tributyl phosphate binds chlorine. After treatment of solution and separation of phases, organic solution is taken for regeneration. For this purpose, it is brought into contact with soda or alkali solution, providing therewith chloride ion removal in form of aqueous sodium chloride solution and recovery of initial hypochloric acid solution in tributyl phosphate.

EFFECT: invention allows to increase efficiency of cleaning sulphate or nitrate solutions from chloride ion.

1 cl, 6 ex

Description

The invention relates to the field of non-ferrous metallurgy and is intended to remove chloride ion from sulfate or nitric acid solutions of various compositions.

Purification from chlorides is a common task and is due to the interfering effect of chloride ions on a number of hydrometallurgical processes, a decrease in the quality of marketable products due to chloride impurities, an increase in the corrosion activity of production solutions, etc.

A known method of removing chloride ion from zinc sulfate solutions, including the addition of copper sulfate and the precipitation of chloride ion in the form of an insoluble precipitate of CuCl. As reducing agents of copper (2+) to copper (1+), powders of metallic zinc, aluminum, magnesium or iron are used [Japanese Patent No. 59-81880, publ. 11/13/85]. The disadvantage of this method is the use of expensive metal powders to restore copper (2+) to copper (1+), which forms an insoluble compound with chloride ion, contamination of the electrolyte with extraneous elements (copper, etc.).

Known methods for the purification of zinc sulfate solutions from chloride ions by copper cake precipitation [RF No. 2372413 C1, publ. 11/10/2009; Syroeshkin M.E., Yumakaev Sh.I. Processing of Waelz-oxides, slag pulps and lead dust in lead-zinc plants. M .: Metallurgy. - 1972. - p. 88. - S. 48-57]. The disadvantages of the proposed methods is the partial coprecipitation and loss of zinc and cadmium with copper-chlorine cake, as well as the long duration of the cleaning process.

Closest to the proposed invention in technical essence is a method of purification of zinc sulfate solutions from chloride ions by extraction with quaternary ammonium base sulfate in an organic solvent in the presence of phenol derivatives [A.S. USSR No. 861313, publ. 09/07/81]. The method consists in extracting the chloride ion with a quaternary amine salt, followed by reextraction of the halide ions with an alkaline solution and treating the organic phase with sulfuric acid.

The disadvantage of this method is its low efficiency for the processing of nitrate and sulfate solutions, due to the low separation coefficients of chloride / nitrate and chloride / bisulfate - anions.

The objectives of the invention is to increase the efficiency of purification from chloride ion of sulfate or nitrate solutions.

The technical result is achieved by the fact that the chloride-containing technological solution is contacted with a solution of hypochlorous acid (HOCl) in tributyl phosphate (TBP). Due to the high oxidizing potential of the extractant [Study of the redox properties of the system "aqueous solution-tributyl phosphate-hypochlorous acid" p. 241-245; Kuzmin D.V .; Kuzmin V.I .; Pashkov G.L. - SFU Journal - Chemistry Series (Volume 2, Number 3) - September 2009] The chloride ion is oxidized to form elemental chlorine (1). A large depth of chlorine removal is achieved by binding chlorine TBP (1) or its simultaneous air blowing

where the symbols (c) and (o) denote the component belongs to the aqueous or organic phases, respectively.

After cleaning the solution and separating the phases, the organic solution is sent for regeneration. To do this, it is contacted with a solution of soda or alkali (sodium hydroxide), which ensures the removal of chloride ion in the form of an aqueous solution of sodium chloride and the restoration of the initial solution of hypochlorous acid in TBP - reactions (2) and (3)

According to another scheme, chlorine from the organic phase is blown off with air (4) or carbon dioxide, then it is absorbed from the gas phase at the stage of extractant regeneration by contacting with TBP solution and aqueous solutions of soda or sodium hydroxide (5)

where the symbol (g) means gas phase

The developed method is confirmed by examples.

Example 1. A purified aqueous solution containing 1 mol / L H ₂ SO ₄ and 0.1 mol / L HCl was mixed with an organic solution containing 0.15 mol / L HClO in TBP for 15 minutes. The ratio of aqueous and organic phases is 1: 1, room temperature. As a result of extraction, an aqueous solution is obtained containing less than 0.001 mol / L Cl - and elemental chlorine, which corresponds to the extraction of chlorine above 99%.

Example 2. The treatment of an aqueous solution is carried out under the same conditions, except that to reduce the viscosity of the organic phase, a solution of hypochlorous acid in 80% TBP in a hydrocarbon diluent (heptane) is used. The recovery of chlorine from the solution is also more than 99%.

Example 3. A purified aqueous solution containing 3 mol / L HNO ₃ and 0.5 mol / L HCl was mixed with an organic solution containing 1.2 mol / L HClO in TBP for 15 minutes. The ratio of aqueous and organic phases is 2: 1. As a result of extraction, an aqueous solution is obtained containing less than 0.001 mol / L Cl ^- - 99.8% chlorine recovery.

Example 4. A purified aqueous solution containing 0.5 mol / L NiSO ₄ , 0.5 mol / L CuSO ₄ , 1M H ₂ SO ₄ and 0.1 mol / L HCl, mixed with an organic solution containing 0.15 mol / l HClO in TBP for 15 minutes. As a result of extraction, an aqueous solution containing 0.005 mol / L Cl ^{- is} obtained. Chlorine recovery from this complex solution is 95%.

Example 5. An aqueous sulfate solution containing 0.52 mol / L hydrochloric acid is contacted with a 0.52 M solution of hypochlorous acid in 80% TBP in a hydrocarbon diluent (heptane) with equal phase volumes.

Then the organic phase is shaken with a 0.52 mol / L soda solution at equal volumes of phases. As a result of reextraction, an aqueous solution containing 0.52 mol / L Cl- and an organic solution containing 0.49 mol / L hypochlorous acid are obtained. The regeneration of the extractant was 95%.

Example 6. The chlorine-saturated organic phase, according to example 5, is contacted with a solution of sodium hydroxide with a concentration of 0.52 mol / l at equal ratios of phase volumes. An aqueous solution of sodium chloride with a concentration of 0.52 mol / L and an organic solution containing 0.51 mol / L of hypochlorous acid are obtained. The regeneration of the extractant was 98%.

Thus, the proposed method allows for effective cleaning of chloride ion of sulfate, nitrate or other complex salt solutions. The process is very efficient, and the extraction of chloride ion in 1 step reaches 99% or more, even at high concentrations of chloride ion in the initial solution. Almost complete regeneration of the extractant is easily achieved in 1 step of processing the organic phase with alkaline reagents (sodium hydroxide, soda), taken in an equivalent amount to wash out the chloride ion from the organic phase.

Claims (1)

The method of purification of sulfuric acid or nitric acid solutions from chloride ion by extraction, characterized in that the chloride ion is removed from acidic media with a solution of hypochlorous acid in tributyl phosphate followed by regeneration of the extractant, treatment of the organic phase with aqueous solutions containing sodium hydroxide or soda, taken in an equivalent amount of in relation to chloride ion.